Looking at your save it seems to me that you've done everything you can do, you should drop the flyer in the mailbox.
(keep a Pre-Calendar save)
I'm not sure why she isn't spawning in the bathroom, it might be because you cheated her stats (it might have been a case of Bathroom at < n, Laundry at > n)
I don't think it is a big deal at this point, you get more advanced bathroom scenes after the photo shoot and can access the earlier ones then too. Connies Dinner is another you can't do till after the Calendar shoot.
Edit: Confirmed I dropped Dorothy's Corruption & Love to 10 and she started spawning in the Bathroom, looks like it is just a peepshow at this stage, more happens after the photoshoot.